Lecture 2 HIV Hep C

Question 1

What is the definition of a virus?

Answer 1

A non-cellular micro-organism that can only replicate within cells

Question 2

What does it mean by ‘obligate intracellular parasites’?

Answer 2

Has to be inside the cell to replicate

Question 3

Describe the structure of a virus

Answer 3

protein coat (capsid) surrounding a nucleic acid genome 
Can be enveloped = surrounded by lipid membrane, may have glycoproteins on the membrane to interact with the host cells 
non enveloped = only a protein and genome 
[see slide for image]

Question 4

Is the genome made from DNA or RNA?

Answer 4

Depends on virus, can be either

Also can be single stranded, duplex, circular or linear

Question 5

Described the simplified virus life cycle

Answer 5

Cell entry → RNA/protein synthesis → genome replication → protein synthesis → assembly of infectious virus particles → release from the cell (cycles back to cell entry)

Question 6

What does a virus need from the host cells?

Answer 6

Raw materials for synthesis of biomolecules (proteins) e.g. nucelotides, amino acids
Machinery for synthesis of biomolecules e.g. protein synthesis requires hosts ribosomes as the virus does not have any
Enveloped viruses need membranes
Transport around the cell
Life! - viruses cannot replicate in a dead cell

Question 7

What are the ideal characteristics of antiviral drugs?

Answer 7

Cell membrane is permeable
No activity against cellular targets - needs specificity
Inhibition of virus encoded protein/virus specific function/process - specificity
Targets critical stage of virus life cycle
No resistance

Question 8

What is HIV?

Answer 8

Human immunodeficiency virus
Causes acquired immunodeficiency syndrome (AIDS)
RNA retrovirus

Question 9

Which cells does HIV infect?

Answer 9

CD4+ cells e.g. T-lymphocytes
Macrophages
Dendritic cells

Question 10

How is HIV defined by WHO?

Answer 10

Progressive qualitative and quantitative decline in CD4+ lymphocytes

Question 11

How many types of HIV is there and which is more harmful?

Answer 11

HIV 1 = human aids

HIV 2 = also causes immunosuppression but less harmful, mainly in africa

Question 12

Which area of the world has the highest death rate in 2016 from HIV/AIDS

Answer 12

Sub saharan africa - also the biggest decline in deaths

Question 13

Which area of the world has the highest newly infected rate in 2016 from HIV/AIDS

Answer 13

Sub Saharan africa - though it is reducing

Question 14

Explain the trend in the number of people accessing antiretroviral therapy

Answer 14

Increasing in number

20 million treated out of 35 million suffering

Question 15

What are the 3 stages of the course of the HIV infection?

Answer 15

1) primary phase illness
2) Asymptomatic stage
3) AIDS

Question 16

What is viraemia?

Answer 16

the presence of viruses in the blood

High = high infection

Question 17

Explain what happens in the primary illness phase

Answer 17

Influenza like illness - virons distribute throughout the body
Sharp rise in viraemia
Increase in HIV specific cytotoxic level = effective at reducing viraemia
Antibodies produced
[See slide for image]

Question 18

What is the relevance of the set point?

Answer 18

The lower the set point, the greater the chance of survival of the patient

Question 19

Explain what happens in the asymptomatic phase

Answer 19

~10+ years
Immune response is controlling the viraemia level well - cytotoxic level stable and high, viraemia stable and low
Antibody level stable
[See slide for image]

Question 20

Explain what happens in the AIDS phase

Answer 20

Viraemia increases rapidly and CD4 level decreases as well as cytotoxic cells and antibodies
Death around 2 years later
[See slide for image]

Question 21

What is the structure of a HIV particle?

Answer 21

Enveloped virus
2 copies of RNA
[see slide for image]

Question 22

What enzyme is responsible for transcribing the viral RNA into double-stranded DNA? What is this process known as?

Answer 22

Reverse transcription

Question 23

Explain the HIV life cycle

Answer 23

HIV virus binds and fuses with host cells membrane → RNA is converted into DNA via reverse transcriptase → DNA enters the nucleus via intergrase enzyme → DNA is transcribed and translated to form viron → maturation of viron occurs via protease enzyme = now infective

Question 24

What enzyme is inhibited by NRTI/NNRTI’s?

Answer 24

reverse transcriptase

Question 25

What 3 classes of drugs are licensed to treat HIV?

Answer 25

Nucleoside analogue reverse transcriptase inhibitors (NRTIs) Non nucleoside analogue reverse transcriptase inhibitors (NNRTIs) Protease inhibitors (PI)

Question 26

What is HAART?

Answer 26

Highly active retroviral therapy Triple therapy Usually 2 NRTI's and NNRTI or PI

Question 27

How long is HAART treatment given for?

Answer 27

lifetime therapy | reduces viraemia in 8 weeks

Question 28

Name 4 examples of NNRTIs

Answer 28

Nevirapine Etravirine Delavirdine Efavirenz

Question 29

How do NNRTIs work?

Answer 29

Inhibits reverse transcriptase by binding to the allosteric site Does not stop thymidine binding unlike NRTIs

Question 30

Name 3 examples of NRTIs

Answer 30

Azidothymidine (AZT) 2',3'-dideoxyinosine (ddl) - analogue of adenosine Dideoxycytidine (ddC) - analogue of deoxycytidine

Question 31

How do NRTIs work?

Answer 31

analogue of thymidine - 100 fold more affinity for reverse transcriptase than cellular polymerases (so not that specific) = chain termination

Question 32

Can you treat with NNRTIs and NRTIs at the same time?

Answer 32

Yes as they both target reverse transcriptase but in different ways Reduces chance of resistance

Question 33

Explain the process of HIV maturation

Answer 33

Budding of the cell occurs which shows electron dense material on the outside of the cell The virus is released and Gag and Gag-Pol is cleaved by the protease enzyme into individual proteins = electron dense material now in the middle [see slide for image]

Question 34

Name 2 examples of protease inhibitors

Answer 34

Saquinavir | Nelfinavir

Question 35

How does the protease inhibitor class work?

Answer 35

Competes with the peptide the protease enzyme normally cleves Protease inhibitors are membrane permeable to be able to target the virus Protease is unique to virus = specific

Question 36

What are 3 pros to HAART therapy?

Answer 36

Manipulate treatment to avoid resistance Treatment interruptions - stopping the medication for a period of time when the patients develops resistance so that the resistant virus have to compete with all the other viruses and the number reduces Highly effective at reducing viral load and disease progression

Question 37

What are 5 cons to HAART therapy?

Answer 37

``` Cost Compliance - effects lifestyle Side effects Drug-drug interactions Post therapy reversion - removing the patient off the drug = viral load increases ```

Question 38

How many people does WHO estimate to be infected with Hep C?

Answer 38

73 million

Question 39

Which is more prevalent, HIV or Hep C?

Answer 39

Hep C - 6 million new infections per year

Question 40

What are the consequences of Hep C virus?

Answer 40

Chronic liver disease i.e. Fibrosis, cirrhosis and hepatocellular carcinoma

Question 41

What is the most common genome group of Hep C?

Answer 41

1 | Very variable and can mutate easily

Question 42

What is the most problematic genome group of Hep C in the UK?

Answer 42

3

Question 43

What percentage of people with Hep C go on to have the chronic infection

Answer 43

85%

Question 44

What does the NS3 gene code for? | NS = non functional

Answer 44

protease and helicases | Therefore cleaving and separating strands of DNA

Question 45

What does the NS5B gene code for? | NS = non functional

Answer 45

RNA dependent RNA polymerase - makes RNA copies of the RNA genome Differs from HIV polymerase as makes RNA not DNA

Question 46

What does the NS5A gene code for? | NS = non functional

Answer 46

Not sure as no enzymatic activity but still used as a drug target

Question 47

Explain the Hep C replication cycle

Answer 47

Virus binds and enters cell via endocytosis → uncoating → translation and polyprotein processing/RNA replication → virus budding into intracellular vessicles → transported outside of the cell to fuse to the membrane and release NOTE: no maturation is required, the virus is already infective

Question 48

Give 2 examples of 1st generation NS3 proteases

Answer 48

Telaprevir | Boceprevir

Question 49

Give an example of a 2nd generation NS3 proteases

Answer 49

Simeprevir

Question 50

What are the characteristics of 1st generation NS3 proteases?

Answer 50

Potent Prone to resistance Specific to genotype 1

Question 51

What are the characteristics of 2nd generation NS3 proteases?

Answer 51

Potent Effective against first generation resistance Effective against some other genotypes but not GT3

Question 52

Name 2 examples of 1st generation NS5A inhibitors

Answer 52

Daclatasvir | Ledipasvir

Question 53

How do NS5A inhibitors work?

Answer 53

``` predicted to target specifically domain I protein of NS5A which has roles in: Virus RNA replication (with domain 2) Virus assembly (with domain 3) Binding to viral RNA (all domains) Binding multiple cellular factors ```

Question 54

How potent are NS5A inhibitors?

Answer 54

HIGHLY! very low dose of drug needed

Question 55

Name an example of 2nd generation NS5A inhibitor

Answer 55

velpatasvir | Pan genotypic

Question 56

Name an example of a NS5B inhibitor and how it works

Answer 56

Sofosbuvir | RNA polymerase production is inhibited

Question 57

What is the guideline treatment for Hep C genotypes 1-12 via NICE recommendations?

Answer 57

Sofosbuvir (NS5B) + Velapatasvir (NS5A)

Question 58

What is the guideline treatment for Hep C genotypes 1-12 via FDA recommendations?

Answer 58

Sofosbuvir (NS5B) + Velapatasvir (NS5A) + Voxilaprevir (NS3)

Question 59

What is around the total cost of Hep C treatment for 12 weeks?

Answer 59

£40000